mcp-tool-definition-fast-building-an-mcp-server-that-exposes-tools-with-cle-6a0aab0a

THEN Use the FastMCP class from the MCP Python SDK to define tools via the @mcp.tool() decorator. Leverage Python type hints and docstrings to automatically generate tool definitions without manual schema writing. The function name becomes the tool name, and docstring arguments are parsed.

from mcp.server.fastmcp import FastMCP

mcp = FastMCP("weather")

@mcp.tool()
async def get_alerts(state: str) -> str:
    """Get weather alerts for a US state.

    Args:
        state: Two-letter US state code (e.g. CA, NY)
    """
    # tool logic
    return result